Dental Literature Watch · Trial · Prosthodontics
Sleep Bruxism Did Not Break Ceramic Molar Crowns Over Three Years
TL;DR
- Bruxism is routinely treated as a relative contraindication to ceramic crowns. This trial tested that assumption with objective diagnosis.
- Four groups: lithium disilicate and zirconia molar crowns, each in bruxers and non-bruxers.
- No technical complications occurred in any group over three years.
- Survival 95–100% across all four groups, with no significant differences.
- Success rates were numerically lower in the bruxism groups (81.5% vs 95.2% for lithium disilicate) but not statistically significant.
- Crucially, no protective occlusal guards were allowed — this is ceramic in bruxers with no night guard.
The study
| Design | Prospective clinical study with randomised crown-material allocation, 3 years |
| Sample | 109 patients needing a single molar crown. LiDi-SB 27, LiDi-no SB 21, Zir-SB 21, Zir-no SB 24 |
| Bruxism diagnosis | Structured questionnaire + clinical examination + portable electromyography (BruxOff) |
| Technical complications | None, in any group |
| Survival | LiDi 96.3% (SB) / 100% (no SB); Zir 95.2% (SB) / 95.8% (no SB); all p > 0.999 |
| Success | LiDi 81.5% (SB) / 95.2% (no SB), p = 0.211; Zir 85.7% (SB) / 95.8% (no SB), p = 0.326 |
💎 Insight — what this means chairside
Objective diagnosis is what makes this trial worth reading
Most bruxism studies rely on self-report and wear facets, which misclassify heavily.
Adding portable electromyography means the bruxer groups here were genuinely bruxers.
Most bruxism studies rely on self-report and wear facets, which misclassify heavily.
Adding portable electromyography means the bruxer groups here were genuinely bruxers.
The no-night-guard design is deliberate and useful
Withholding the protection you would normally provide is the only way to isolate the material question.
It also means the real-world patient, who does get a guard, should do at least as well.
Withholding the protection you would normally provide is the only way to isolate the material question.
It also means the real-world patient, who does get a guard, should do at least as well.
Watch the gap between survival and success
Survival means the crown is still there; success means it is still there without any problem.
Success was 10–14 points lower in the bruxers — not statistically significant in a trial this size, but not nothing either.
Survival means the crown is still there; success means it is still there without any problem.
Success was 10–14 points lower in the bruxers — not statistically significant in a trial this size, but not nothing either.
⚠️ The catch
Roughly 20–27 patients per group
With zero technical complications anywhere, this trial has almost no power to detect a difference in a rare event.
"No difference found" here largely means "too few events to find one".
With zero technical complications anywhere, this trial has almost no power to detect a difference in a rare event.
"No difference found" here largely means "too few events to find one".
Single molar crowns, three years
Not full-arch rehabilitation, not bridges, not veneers, and not the ten-year horizon over which ceramic fatigue failures accumulate.
Not full-arch rehabilitation, not bridges, not veneers, and not the ten-year horizon over which ceramic fatigue failures accumulate.
The success-rate gap deserves honest framing
An absolute difference of 10–14 percentage points that misses significance in a small trial is a signal to watch, not a finding to dismiss.
An absolute difference of 10–14 percentage points that misses significance in a small trial is a signal to watch, not a finding to dismiss.
⚡ Bottom line
- Confirmed bruxer needing a single molar crown → ceramic is reasonable; no complications at three years even without a guard.
- Choosing between lithium disilicate and zirconia → neither was penalised by bruxism in this trial.
- Still make the guard → the trial withheld guards to answer a research question, not to recommend withholding them.
- Full-mouth rehabilitation in a severe bruxer → well outside this evidence.
🧪 Questions
Tap an answer — instant grade, deciding line, and the trap.
A 44-year-old with electromyography-confirmed sleep bruxism needs a crown on a lower first molar. He asks whether his grinding means he should have metal rather than ceramic. Based on the 2026 three-year trial, what is the most accurate response?
Deciding line: the trial found no technical complications in any of the four groups over three years with guards deliberately withheld, so ceramic is defensible while normal protective practice still applies. Trap: the third option is the engineered trap because it misreads a design choice as a finding, since guards were withheld to isolate the material variable rather than tested and found useless; splitting the two ceramics contradicts a trial in which both performed equivalently.